Field of the Invention
The disclosed and claimed concept relates to a can bodymaker tool pack structured to form a cup-shaped body and, more specifically, to a cooling gas system for the can bodymaker tool pack.
Background Information
It is known in the container-forming art to form two-piece containers, e.g., cans, in which the walls and bottom of the container are a one-piece cup-shaped body, and the top or end closure is a separate piece. After the container is filled, the two pieces are joined and sealed, thereby completing the container.
Cups are formed in a can bodymaker having a tool pack structured to form the cup-shaped body from sheet material. That is, the cup-shaped body typically begins as a flat material, typically metal, either in sheet or coil form. Blanks, i.e., disks, are cut from the sheet stock and then drawn into a cup. That is, by moving the disk through a series of dies while disposed over a ram or punch, the disk is shaped into a cup having a bottom and a depending sidewall. The cup may be initially formed in one bodymaker and transferred to another to be drawn into an elongated can, or, the cup may be formed and drawn into a can within a single bodymaker.
In forming the can, the cup may be drawn through additional dies to reach a selected length and wall thickness. This may be followed by forming an inwardly extending dome to the bottom of the can. That is, the can is moved into engagement with a domer; the domer having a domed end onto which the can is pressed. This action typically occurs at the end of the stroke of the punch. After the dome is formed, the can is removed from the punch for further processing.
This process is a repeating process and, as such, a reciprocating ram is used. For example, assuming that the cup is formed and disposed on the ram to be drawn into a can, the process typically includes the following steps. The ram moves forward during a forming stroke thereby passing the cup through at least one die pack. The die pack includes a die ring. The radius of the opening in the die ring is slightly larger than the radius of the punch. The radius of the opening in the die ring is, however, slightly smaller than the radius of the can disposed on the punch. Thus, as the punch moves through the die ring, the cup is deformed and, more specifically, the cup is elongated axially thereby thinning the sidewall so that the cup may pass through the die ring. The punch and cup may pass through one or more die rings within the die pack.
This process generates heat from friction that is undesirable. As such, the ram, punch, and die pack need to be cooled. Further, it is desirable to reduce the friction before heat is generated. It is known to spray a cooling liquid, e.g., water, oil, or an oil in water emulsion, onto the punch and die pack during operation. Thermal conductivity of the water cools the punch and die pack and use of the oil reduces friction. Such cooling liquids, however, have undesirable qualities. For example, oil in water emulsions may degrade over time as a result of microbial attack or hard water ion accumulation. Further, if the mixture contains toxic additives, the liquid may pose a waste treatment problem.
It is known that a supercritical fluid may be used in place of a cooling liquid in many metal working operations. The supercritical fluid, such as, but not limited to super critical CO2 may be infused with a lubricant as well. Systems for creating, manipulating and applying supercritical fluids are expensive, however. Further, in the context of a bodymaker, a sprayed supercritical fluid would be applied to the punch and die pack as a liquid and, more specifically, micro-drops. The micro-drops of the supercritical fluid would evaporate almost instantly causing localized cooling rather than a substantially even cooling over the surface of the punch and die pack. Further, the lubricant, if used, builds up on the components and eventually breaks down physically/chemically leaving a residue that must be cleaned.